Choroidal thickness in geographic atrophy secondary to age-related macular degeneration.

PURPOSE To analyze choroidal thickness (CT) in eyes with geographic atrophy (GA) secondary to age-related macular degeneration (AMD). METHODS A total of 72 eyes of 72 patients (mean age, 75.97 ± 7.09 years) with GA and 37 eyes of 37 healthy controls (73.89 ± 6.19 years) were examined by confocal scanning laser ophthalmoscopy and enhanced depth imaging (EDI) spectral-domain optical coherence tomography. Choroidal thickness was measured at 25 defined points in horizontal and vertical scans. Geographic atrophy size was determined in fundus autofluorescence (FAF) images and GA subtypes were classified based on abnormal FAF in the perilesional zone. RESULTS In GA, subfoveal CT (fCT) was significantly thinner compared to controls (173.03 ± 90.22 vs. 253.95 ± 69.19 μm, P < 0.001). Analysis of averaged measurements of all 25 points obtained per patient (mCT) revealed similar results (162.07 ± 76.26 vs. 228.00 ± 66.24 μm, P < 0.001). Spatial differences in CT between both groups were largest superior to the fovea. Addressing "diffuse-trickling" (n = 15) and "non-diffuse-trickling" (n = 57) GA independently, fCT was 114.67 ± 43.32 and 188.39 ± 93.26 μm, respectively (P = 0.002), with both groups being significantly thinner than controls (P < 0.001 for "diffuse-trickling" and P < 0.001 for "?non-diffuse-trickling"). Similar results were obtained for mCT, which was 110.21 ± 29.66 μm in "diffuse-trickling," 175.72 ± 79.02 μm in "?non-diffuse-trickling" and 228.00 ± 66.24 μm in controls. Differences were significant with P = 0.002 between both GA groups and P ≤ 0.001 toward controls for each GA group. CONCLUSIONS The results indicate that the choroid in eyes with GA is thinner compared to normal eyes of similar age. Hereby, the extent of thinning is most pronounced in a specific subtype of GA identified by FAF imaging ("diffuse trickling"). Such GA subtype-related differences in choroidal thickness may reflect heterogeneity in the pathogenesis of disease. (ClinicalTrials.gov number, NCT02051998.).